The compound shown is 2-isopropyl-5-methylcyclohexan-1-ol (the menthol skeleton) drawn without stereochemistry. How many stereocentres does it have? Give an integer.

Ring carbons C1 (bearing $\mathrm{OH}$), C2 (bearing isopropyl) and C5 (bearing $\mathrm{CH}{}_3$) each carry $\mathrm{H}$, the substituent and two different ring arms (the two directions round the ring are not equivalent because the other substituents sit at different distances). The isopropyl carbon has two identical methyls and is not a stereocentre, and the $\mathrm{CH}{}_2$ carbons are not either. So there are 3 stereocentres and $2^3=8$ stereoisomers (menthol is one of them).